BULK COLLECT子句使用方法(转)

Using the BULK COLLECT Clause

The keywords BULK COLLECT tell the SQL engine to bulk-bind output collections
before returning them to the PL/SQL engine. You can use these keywords in the
SELECT INTO, FETCH INTO, and RETURNING INTO clauses. Here is the syntax:
... BULK COLLECT INTO collection_name[, collection_name] ...
The SQL engine bulk-binds all collections referenced in the INTO list. The
corresponding columns can store scalar or composite values including objects. In
the following example, the SQL engine loads the entire empno and ename database
columns into nested tables before returning the tables to the PL/SQL engine:
DECLARE
TYPE NumTab IS TABLE OF emp.empno%TYPE;
TYPE NameTab IS TABLE OF emp.ename%TYPE;
enums NumTab; -- no need to initialize
names NameTab;
BEGIN
SELECT empno, ename BULK COLLECT INTO enums, names FROM emp;
...
END;
In the next example, the SQL engine loads all the values in an object column into a
nested table before returning the table to the PL/SQL engine:
CREATE TYPE Coords AS OBJECT (x NUMBER, y NUMBER);
CREATE TABLE grid (num NUMBER, loc Coords);
INSERT INTO grid VALUES(10, Coords(1,2));
INSERT INTO grid VALUES(20, Coords(3,4));
DECLARE
TYPE CoordsTab IS TABLE OF Coords;
pairs CoordsTab;
BEGIN
SELECT loc BULK COLLECT INTO pairs FROM grid;
-- now pairs contains (1,2) and (3,4)
END;
Using the BULK COLLECT Clause
4-38 PL/SQL User’s Guide and Reference
The SQL engine initializes and extends collections for you. (However, it cannot
extend varrays beyond their maximum size.) Then, starting at index 1, it inserts
elements consecutively and overwrites any pre-existent elements.
The SQL engine bulk-binds entire database columns. So, if a table has 50,000 rows,
the engine loads 50,000 column values into the target collection. However, you can
use the pseudocolumn ROWNUM to limit the number of rows processed. In the
following example, you limit the number of rows to 100:
DECLARE
TYPE SalList IS TABLE OF emp.sal%TYPE;
sals SalList;

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